Richard Stallman <rms@gnu.org> writes:

Hi Richard,

I proposed the feature/patch.

I happen to use macOS for my work and of course Emacs (big fan) 
for a bunch of things.

> Could someone please explain briefly what the "native sharing 
> dialog"
> of MacOS does?

May be simpler to visualize. I've attached two screenshots with 
the agreed flow implemented for both GNU/Linux (linux.jpg) and 
macOS (macos.jpg).

>   What does it try to share, and when?

Current buffer file, a selection of files from dired, or region 
text, after the user chooses to share with external apps 
(non-Emacs) via the mouse context menu "Share...".

> When this discussion started, I did not know what sort of 
> feature it
> was asking to enable on MacOS.  I am trying to guess but I am 
> still
> not sure.

I hope the screenshots help here.

> Is it a facility to copy files between one MacOS machine and 
> another,
> that does not communicate with any other system?  I am starting 
> to
> guess so, because a facility that is "native" to MacOS would 
> work only
> on MacOS.

While my initial proposal was for macOS only, I agreed with Stefan 
and Eli in this thread to bring the "Share..." context menu option 
to both GNU/Linux and macOS.